It's not as warm outside as home.

It means that nothing outside is as warm as home. No matter how good the wine outside is, it is not as good as a bowl of noodles at home. No matter how good the wine outside is, it is not as satisfying and warm as eating a bowl of noodles at home. It emphasizes the importance of family and the peace of mind and happiness brought by family. The warmth of family is more precious than the enjoyment outside.